


Pieces of you

by Askellie



Category: Undertale (Video Game)
Genre: Begging, Dominance, Ecto-Genitalia (Undertale), M/M, Masochism, Offscreen deaths of the human child, Oviposition, Ownership, Painful Sex, Punishment, Tentacles, Violence
Language: English
Status: Completed
Published: 2020-09-14
Updated: 2020-09-14
Packaged: 2021-03-06 19:34:21
Rating: Explicit
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 1,631
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26460469
Author URL: https://archiveofourown.org/users/Askellie/pseuds/Askellie
Summary: “Perhaps this is a better use for you. I could simply keep you in my bed, use your body as I please. Would you like that, Killer?”Killer's always had trouble following orders, but how can you blame him when it's so much more fun to be on the Boss's bad side?
Relationships: Kight - Relationship, NightKiller, Nightmare (Dreamtale) / Killer, Nightmare/Killer, Sans/Sans (Undertale)
Comments: 6
Kudos: 258





	Pieces of you

When the first call came, Killer ignored it as he often did, although in this instance he was actually doing his job. He finally had the kid cornered in the Judgement Hall, and was enjoying the way their small body trembled as the determination started to fade from their eyes. Their shock was downright hilarious. They’d tried so hard to be good, to be kind and patient and make friends with everyone only for their good pal  _ Sans _ to block their journey to the barrier and what should have been their ultimate reward.

Instead, what they got was death; slow, painful, miserable, unavoidable. With every reset he could see them losing hope of ever finding a good ending this way. Pretty soon they’d either run out of reasons to keep coming back, or they’d reset from the beginning and try something different -- hopefully paying back the pain he’d caused them in kind on the rest of the monster species. Either way, this would never be a pacifist timeline.

**_Killer._ **

Nightmare’s voice was an irate murmur echoing from the darkness inside his skull. It was louder this time, more insistent. Killer’s expression almost faltered in annoyance. Even though he’d done this song and dance with the human child countless times, this was the part he liked best -- the moment they broke. Watching their hopes shatter stirred something in his own soul, one of those faint emotions he rarely felt anymore. He didn’t want to miss it.

But then again, if the Boss was calling, there might be something even better in store for him so he probably shouldn’t drag out his fun too much.

“It’s a beautiful day outside,” he began, drawing his knife with slow anticipation so he could enjoy the frantic terror in the human’s eyes. It was real, unlike the plastic one in the human’s hand. “Birds are singing. Flowers are-urk!”

The floor suddenly dropped out from under him, his own shadow blooming outward like an inky bloodstain before it swallowed him up like quicksand. He was already sunk up to his knees before he realised what was happening, and in the next moment he was dragged into a thick, murky darkness. It was suffocating, lightless and disorienting, but it only lasted for the span of a breath before he was spat out painfully onto a hard stone floor. The landing was rough -- deliberately so. Nightmare could manipulate the momentum and the orientation of his portals, so dumping Killer out onto his back with enough force to bruise was both deliberate and spiteful.

“Really, Boss?” He asked, looking up piteously at the unsympathetic ceiling. A moment later, Nightmare was leaning over him, his expression clouded with delightful aggravation

“I called you,” Nightmare growled. “Twice.”

Killer beamed brightly. “Did you? Wow, I must have been real busy if I didn’t answer straight away.”

Nightmare’s expression darkened. His tentacles seethed around him like angry snakes, dripping with ooze like they were spitting venom. “You seem to have forgotten who you belong to. Must I remind you again?”

The tone of his voice gave Killer a better shiver than the human’s distraught expression ever could. The jerk of shock as his clothes were roughly torn off his body was even better. He smirked widely, deliberately splaying his naked bones against the floor in a shameless, dangerous offering. “Aww, did you miss me that much? If I’d known you were feeling needy I’d have come back sooner.”

Teasing Nightmare when he was already in trouble wasn’t always a smart idea, but Killer couldn’t seem to help himself. It was too gratifying to feel the possessive way Nightmare’s tentacles spread his legs apart and thrust through his empty pelvis. The rough friction burned, his grin straining as he bucked against the floor. A second cruel thrust made him gasp, rutting shamelessly down on that friction. 

The human kid had never gained any LV, and even when they’d finally tried fighting back, they simply couldn’t land a satisfying hit on Killer even when he gave them a free shot. Their puny plastic knife simply bounced off him ineffectively. Nightmare, however, is an expert on pain, and he knows Killer’s every weakness. The underside of his pubic symphysis is already flaring red, hot and bruised as the tentacle drags cruelly along its groove. The moan that slips out of him is unintended and almost desperately wanton. 

Nightmare looked down at him, his expression pitiless. “Perhaps this is a better use for you. I could simply keep you in my bed, use your body as I please. Would you like that, Killer?

The remaining tentacles coiled around Killer’s limbs and turned him over, forcing him down onto his hands and knees with his face pressed submissively into the floor. One of them kept a tight hold on the back of his neck, grinding his cheek down against the bare stone with a scrape that feels as sweet as a kiss. The pressure in his pelvis eased slightly as Nightmare withdrew his penetrating coils, and the moment Killer’s magic had the freedom to form it dropped urgently into place.

“Shameless,” Nightmare scoffed, running the tip of a tendril up between Killer’s slit. “You seem to like the idea. I can feel how wet you are already.”

Killer’s bones rattled noisily as Nightmare stroked him carefully, a teasing, light touch that made him yearn for the pain. Nightmare chuckled darkly. “You want me to stake my claim? So be it.”

There was a bizarre sound behind him, like the tearing of wet paper. Killer glanced over his shoulder to find Nightmare plucking off the tip of his tentacle. It came away easily, separating like oil in water, forming a floating ball above his hand. Separated from the rest of Nightmare’s mass, its viscous layer turned hard, gaining a pearl-like sheen as it solidified into a perfect sphere.

“If you’re so eager to have me inside you,” Nightmare said, his smirk a vicious slice of white against the obsidian of his bones, “then let me grant your desire.”

“Ahhh f-fuck,” Killer whined, bracing himself with his forearms as Nightmare knelt down behind him. The flat, unyielding surface of the pearl was set against his pussy, cool and smooth against the heat of his aroused and swollen flesh. Then Nightmare started applying pressure, and Killer could only try to swallow down the humiliating noises he made as the orb was mercilessly forced into his passage.

The meagre slickness he’d had time to generate wasn’t nearly enough to lubricate such a large object. He wasn’t nearly relaxed or loose enough either, and it burned as it forced his unprepared muscles to stretch. Killer gurgled fervently, fingers clawing against the floor as he wailed with each agonising inch of progress the pearl made until it finally reached an impasse that forced his magic to reach. Ecto-flesh coalesced inside his abdomen, filling up the space between his ribs and his pelvis in a rounded cavity to accept the offering of the pearl. It dropped into the created space, creating a distended bump inside his newly formed stomach.

“Did you like that?” Nightmare purred. Dimly, Killer heard the tearing sound again as he extracted another piece of himself in preparation. “I’m happy to give you more.”

The second pearl felt even bigger than the first. If his magic weren’t so resilient, Killer would worry about his cunt being ripped open as the rigid shape was shoved inside him. His pussy clenched tightly with a pinching tension that almost felt like the verge of climax. There was a dark pool under Killer’s face from the overflow of his sockets that always came when he was verging on real emotions. The pain was incredible, utterly perfect. 

“More,” he panted, spreading his legs even further apart. He felt light-headed with beautiful agony. His summoned parts ached with the unfamiliar strain but he could feel his own arousal dripping down to splatter between his bruised knees. “Please-!"

“Tell me, then...who do you belong to?”

“You!” 

Killer wailed in gratitude as another pearl was forced in. This time the texture was less smooth, its outer layer ribbed with tiny, upraised nodes that scraped his passage raw. Killer howled when it finally reached the end of his passage, dropping in beside its brethren. His stomach felt so big and bloated, tender and oversensitive. Everything was throbbing, his bones, his flesh, his soul, all pulsing in a harmonious tempo of pleasure. Distantly, he could feel a tentacle cur around his belly, squeezing it tight enough to make him feel nauseous.

“Good boy.” Unceremoniously, he felt himself being scooped up off the floor and cradled across Nightmare’s lap. “Perhaps if I ever choose to let you leave again, you will have learned your lesson about coming when I call you.”

“Ugh…” Killer sank bonelessly against Nightmare’s shoulder, too exhausted to squirm. He felt wrecked; his bones damp and sticky, his belly protruding with uncomfortable fullness and his cunt still hot and unsatisfied. The glitter of Nightmare’s eye told him he probably wasn’t going to have that need attended any time soon, nor was he likely to have any assistance in removing the pearls unless he made an extremely convincing apology for his insubordination.

But that could wait until later. Right now, the unfamiliar pressure inside him felt almost as good as a proper climax would have. Even better was the look of utter satisfaction on Nightmare’s face as he looked down at the evidence of himself in Killer’s body, thoroughly pleased with himself.

It was worth it, getting to see that particular look on Nightmare’s face, and if it meant he got some unprecedented time off while spending a few days in the boss’s bed for more ‘punishment’, that was even better. 


End file.
